The first attacks on ships in Bulgaria's economic zone came on 6 October, when the Alfa Watan and the Able were hit about 70 nautical miles east of Byala. The Able's whole crew was rescued. The rescue operation for the Alfa Watan's crew was called off, and the crew remain missing.
A week later, on 13 October, drones hit two more vessels. Three drones attacked the Chelsea-3 about 18 miles east of Byala. All sailors on board were rescued.
The HS Dignity sank about 17 nautical miles east of Krapets. Only five of its 16 crew were rescued, and 11 are missing.
After the incidents, the Defence Ministry and the navy raised their alert level. Radar coverage has been expanded, and drones are checking the affected areas.